KYIV, Ukraine — Thousands more civilians have fled Russia’s renewed ground offensive in Ukraine’s northeast that has targeted towns and villages with a barrage of artillery and mortar fire, officials said Sunday. The intense battles have forced at least one Ukrainian unit to withdraw in the Kharkiv region, capitulating more land to Russian forces across less defended settlements in the so-called contested “gray zone” along the Russian border. [time-brightcove not-tgx=”true”] Meanwhile, a 10-story apartment block collapsed in the Russian city of Belgorod, near the border, with several deaths and injuries reported.